In recent years, the installation into vehicles of knee airbag devices for vehicles, that inflate and expand a knee airbag at the time of a collision and restrain the kneecaps (hereinafter simply called “knees”) of a vehicle occupant, is being accelerated from the standpoint of improving the vehicle occupant protecting performance at the time of a collision.
For example, in the knee airbag device for a vehicle for the front passenger's seat that is disclosed in following Patent Document 1 (Japanese Patent Application Laid-Open No. 11-321539), an airbag module is disposed at the knee height of a seated vehicle occupant at an instrument panel, and, at the time of a collision, a knee airbag that is divided into an upper chamber, a central chamber, and a lower chamber is inflated and expanded toward the knees of the vehicle occupant.
Further, in the knee airbag device for a vehicle for the front passenger's seat that is disclosed in following Patent Document 2 (Japanese Patent Application Laid-Open No. 2002-356137), an airbag module is disposed within the glove box door of a glove box. At the time of a collision, gas is jetted-out from an inflator disposed within the glove box door, and a knee airbag, that is accommodated within the glove box door in a folded-up state, is inflated and expanded toward the knees of the vehicle occupant.    Patent Document 1: Japanese Patent Application Laid-Open No. 11-321539    Patent Document 2: Japanese Patent Application Laid-Open No. 2002-356137    Patent Document 3: Japanese Patent Application Laid-Open No. 2006-36141    Patent Document 4: Japanese Patent Application Laid-Open No. 2007-161090